Laminating process and apparatus



Oct. 17, 1967 0. H. HILL 3,347,723

LAMINAT'ING PROCESS AND APPARATUS I Filed April 25, 1963 3 Sheets-Sheet J J/ If J5 I 174/0- hf Hz/Z l Y [71 7X Oct. 17, 1987 D. H. HlLL 3,347,723

LAMINATING PROCESS AND APPARATUS Filed April 25, 1963 3 Sheets-Sheet 2 INVENTOR.

Z419 HZ/Z A 770 FIVE Kg Oct. 17, 1967 D. H. HILL LAMINATING PROCESS AND APPARATUS 3 Sheets-Sheet 3 Filed April 25, 1963 INVENTOR. H #277.

United States Patent 3,347,723 LAMINATING PROCESS AND APPARATUS Dale H. Hill, Farmiugton, Mich., assignor to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Filed Apr. 25, 1963, Ser. No. 275,610 7 Claims. (Cl. 156-403) This invention relates to a continuous three-stage method of laminating glass or similar sheet material.

It is a primary object of this invention to provide a continuous three-stage process that will permit a fast, economical, improved type of lamination by a substantially conventional, yet improved, type of apparatus.

It is another object of this invention to provide an improved apparatus, and specifically an improved autoclave unit, for the lamination of glass sheets or similar materials.

Other objects and advantages of this invention will become readily apparent from a reading of the following description and a consideration of the related drawings, wherein:

FIGURE 1 is a sectional elevational view of an autoclave unit embodying this invention;

FIGURE 2 is a sectional elevational view taken along the line of and looking in the direction of the arrows 22 of FIGURE 1;

FIGURE 3 is a sectional elevational view taken along the line of and looking in the direction of the arrows 33 of FIGURE 1;

FIGURE 4 is a fragmentary sectional elevational view taken along the line of and looking in the direction of the arrows 4-4 of FIGURE 3; and

FIGURE 5 is a diagrammatic side elevational view of the autoclave apparatus and its associated equipment that is utilized in carrying out the process embodying this invention.

As clearly shown in FIGURE 1, this autoclave apparatus involves a cylindrical tank-type autoclave unit A that has a pivoted top 11 supported by the cylindrical tank member 10. Top 11 is hinged to tank as shown at 12 and the top is counterbalanced by the counterweight mechanism 13. Suitable bolt connector means 14 are utilized between the periphery of the hinged top 11 and the tank portion 10 to sealingly lock the top member 11 to the top of the tank member 10 during the several stages of the process to be hereinafter described. It will he noted from FIGURES 1-3 that the cylindrical tank 10 has interiorly disposed, chordal arranged, vertically extending partitions 16, 17, 18 and 19 that provide four vertically extending conduit chambers 21, 22, 23 and 24, respectively. These conduit chambers 21 through 24 are to facilitate the circulation of air and/or gas throughout the autoclave unit during the various stages of the laminating process as will be described hereafter.

Mounted in the lower end of the tank 10 is a base framework composed of a horizontally disposed bottom frame 28 and a horizontally disposed upper frame 29 that are interconnected by substantially vertically extending leg members 30. Extending between and mounted within the upper frame 29 and the lower frame 28 is a funnel-shaped conduit 25 that has a series of fluid circulating coils 47, 48 and 49 mounted in its center section 32. The upper section 31 of the funnel-shaped conduit 25 is provided with a trap door 31a for service purposes. The lower section 33 of the funnel-shaped conduit 25 terminates in an outlet 34 that provides the discharge into a centrifugal fan 50. Fan 50 is connected to a fan shaft 51 that mounts a pulley member 52 that is drivingly connected by means of belts 55 to a suitable motor driven pulley not shown. Drive shaft 51 is encircled by a seal 53, preferably of the 3,347,723 Patented Oct. 17, 1967 ice pressure responsive type. A suitable shaft bearing 54 journals the drive shaft 51.

As previously mentioned, located in the middle section 32 of the funnel-shaped conduit 25 at the lower end of the autoclave tank 10, are three heat transfer coil units 47, 48 and 49, respectively. Each of these coil units has an inlet pipe and an outlet pipe so that heating and/or cooling fluids of various types may be circulated through each of the coil units 47, 48 and 49. In the instance shown, the coil 47 has inlet pipe 41 and outlet pipe 44. The coil unit 48 has inlet pipe 52 and outlet pipe 45. The coil unit 49 has inlet pipe 43 and outlet pipe 46. Each of these several inlet and outlet pipes for the several coil units' 47, 48, 49 are connected through suitable control valving to supply and discharge conduits or manifolds as will be described hereafter.

As can be observed from FIGURE 5, the supply riser 61 is connected to a main valve controlled manifold 69 that is adapted to receive either hot steam from the supply pipe 71 or some type of refrigerant or coolant from the supply pipe 70. Either of these fluids, namely a heating fluid or a cooling fluid, may be introduced into supply riser 61 through the manifold valve 69. Likewise, the fluid supplied through the riser 61 can be selectively introduced into the several coils 47, 48 and 49 by means of the valves 63, 64, 65. The coil supply and discharge risers 61 and 67 are also connected to the inlet and outlet respectively of the coil unit 66 that is mounted for the underside of the autoclave pivoted head 11. A fan unit 68 is positioned adjacent the coil 66 to facilitate heat transfer.

Connected to the interior of the autoclave tank 10 is a conduit 78 such that compressed air or a similar pressurizing fluid medium may be introduced into the tank interior to facilitate the laminating process. In the inr stance shown, the conduit 78 is connected through the tank sidewall 10 (see FIGURE 5) and this conduit is controlled by a valve 79. Conduit 78 is connected through valve 79 to a suitable pressure pump 80 that is adapted to be driven by a motor means 81.

' To initiate a laminating process according to this inven tion the first step is to assemble the materials to be laminated 83, 84 and 85 (see FIGURE 4) into laminating sandwich assemblies W. After assembling the laminate sandwich assemblies, a deairing ring R, which is an endless resilient ring, is applied around the entire periphery of each of the laminate assemblies W. The rings R are completely described in Harvey J. Little, United States Patents Nos. 3,074,466 and 3,074,838. Thereafter groups of these laminate assemblies W with the deairing ring R applied thereto are stacked in the baskets 35, 36, 37 and 38 as shown in FIGURES 1 and 3. From FIGURE 1 it will be noted that the windshield laminate assemblies W with the deairing rings R mounted thereon are arranged in the stacked baskets 35-38 such that the windshield assemblies W in successive baskets are tilted in opposite directions. This facilitates a scrubbing action of the autoclave gases or fluids that are circulated across the windshield assemblies W during the laminating operation. After mounting the ring encircled laminate assemblies W in the baskets 35-38 then the coupling of each ring R is connected to the header pipe 101 on each basket. Each basket header pipe 101 is connected to a riser pipe 102 when the several baskets 35-38 are stacked in the autoclave tank 10. After the several baskets of windshield assemblies W with the deairing rings R applied thereto have been arranged in the autoclave unit A as shown in FIGURE 1, then the various header pipes 101 are connected to the riser pipe 102. Riser 102 is continuously connected by conduit 103 to the evacuation conduit 104. Evacuation conduit 104 is connected through valve means ing operation is then ready to begin. At this time the evacuation pump 75 is brought into operation and an evacuation pressure of approximately 20 to 30 inches of mercury is established within the various deairing.

rings R that surround the laminate assemblies W. At the same time that the. laminate assemblies are being deaired by the evacuation rings R, heat in the form of steam or some other fluid medium is introduced into the several coil elements 47, 48 and 49 at the lower end of the autoclave unit A and heat may also be introduced at this time into the upper coil elements 66 or the underside of the tank lid 11. Along with the introduction of heat in the coil units and suction in the evacuating rings R, there is also a bonding pressure developed within the autoclave unit A. The bonding pressure is accomplished by means of a pressure pump 80 that is connected to the interior of the tank by means of the conduit 78 and valve 79. During this first stage of the laminating operation, if the laminate assembly W is formed of glass sheets 83, 84 with a polyvinyl butyral interlayer 85, a pressure of approximately 50 to 100 pounds per square inch is established within the autoclave unit A by means of the pressure pump 80. The heating medium introduced through the several coil elements 47, 48, 49 and 66 is such as to establish a temperature within the autoclave unit A of somewheres in the range of between 225 F. to 265 F. during the first stage of the laminating operation. With an evacuation pressure of to inches of mercury, a pressure of 50 to 100 pounds per square inch, and a temperature of 225 F. to 265 F., it has been found that in the first stage a pretacking or prepressing of the laminate assemblies can be accomplished within a relatively short period oftime, that is within thirty minutes. While the temperature and pressure values given for this first stage of the laminating operation, that is called the prepress or pretack stage, have been found to establish a satisfactory prepress, it is notto be considered that the ranges indicated are the only ranges that will work. Changes in materials for the interlayer and outside sheets will undoubtedly require changes in the times, pressures and temperatures used in the laminating operation.

The second stage of laminating or the final laminating stage is accomplished without removing the laminate assemblies W from the autoclave A. The second stage is achieved in the following mannerpFirst there is a termination of evacuation through the deairingrings R by connecting the evacuation conduit 104 to atmosphere through operation of the valve 74. At the same time that evacuation through the deairing rings is terminated, the

in the autoclave unit A there is an increase in the temperature within the autoclave unit A to a higher range of between 250 F. to 350 F. With a pressure of approximately 250 pounds per square inch and a temperature of approximately 250 F. to 300 F., the second or bonding stage of the lamination process can be accomplished within thirty-five minutes or less.

On completion of the second stage of the laminating process, the heated fluid supplied to the variouscoil units 47, 48, 49 and 66 is shut off by way of manifold valve 69. Thereafter to facilitate cooling of the laminated assemblies W in the shortest possible time a coolant fluid may be introduced to the coils 47, 48, 49 and 66 by way of supply conduit 70, the manifold valve 69, and the supply riser pipe 61. This coolant fluid is then circulated through the various coil units 47, 48, 49 and so as to provide a fast but a controlled cooling within the autoclave unit A. Controlled cooling will prevent thermal shock that might cause glass cracking due to thermal stresses. The cooling of the'laminate assemblies also.

facilitates their immediate handling when the baskets 35-38 are subsequently removed from the autoclave unit A. It is believed that within twenty-five minutes the.

temperature of the bonded laminate assemblies W can be dropped to less than 150 F. when the cooling stage disclosed is utilized.

When the third or cooling stage of this process is initiated the pressure within the autoclave tank is relieved by suitable control of the pressure pump and the associated valve 79. The reason the pressure is reduced within the tank A during the cooling stage is that the heat transferfluid, that is the air or gas circulated within the tank by fans 50 and/or 68, is higher at the reduced pressure and thus it can be circulated faster. As a result of faster circulation of the heat transfer medium it is possible to achieve a faster cooling of the previously heated laminate assemblies. The evacuation or deairing rings R remain inactive during the cooling stage as .was the case during the second stage bonding or laminating stage. Obviously, if the laminate assemblies have been completely bonded during the second stage then there is no possible need for any deairing during the cooling stage because the glass sheets 83, 84 have already been bonded to the interlayer 85 through the area of the laminate assembly W.

It is thought to be obvious from what has been set forth with respect to the several stages of this multi-stage laminating process that the circulating fans 50 and/or 68 for the heat transfer medium operate during all stages of the laminating process. While these fans can be constant speed units, still, it is possible to improve control of the. laminating process by using variablespeed fans that have thermostatic speed controls associated therewith. In this manner temperature sensors within the tank A can signal the interior temperatures to the fan speed controls and the fans. canoperate more effectively to maintain the desired temperatures during the variousv stages of the laminating process;

One of the important conditions that must be maintained during a laminating operation to achieve maximum yield is that there bea uniform temperature and pressure laminating process in a minimum of time and with the minimum expense and operator supervision.

It will be noted from FIGURES 1 and 5 that the centrifugal fan 50 draws the air or otherheat transfer medium within the autoclave unit A downwardly through the lower end or outlet 34 of the funnel-shaped ducts 25. Air or gas drawn through duct 25 by fan 50 is discharged radially outwardly so that it tends to follow thepath of the arrows 110. The fluid flow path for the heat transfer fluid is relatively well defined by the several vertical chambers 21, 22, 23 and24 which carry the circulating heat transfer fluid from the lower end of the autoclave unit tank 10 upwardly along the tank side wall and discharges it across the top of basket 35 within the autocalve unit. The fluid flow from the top end of tank 10 will be downwardly through the several stacked baskets of laminate assemblies W from Where it will be discharged through the duct section 31 to the coil section 32 and then to the outlet section 33 and back into the fan 50.

While the supplemental heat transfer coil 66 and associated fan 68 that are mounted on the underside of the autoclave lid 11 can be omitted without materially interfering with the operation of the described two-stage laminating process, still, the units 66 and 68 insure maximum and uniform heat transfer within the autoclave unit A and therefore these units 66, 68 form a part of the preferred embodiment of this invention.

Another arrangement of structure that is disclosed in FIGURE 1 and that contributes to the improved heat transfer achieved with this autoclave unit, is the specific arrangement of the windshield laminate assemblies W within the stacked baskets 35-38. By tilting the assemblies W in adjacent stacked baskets in opposite directions, it is possible to give the heat transfer fluid or gas circulated through the autoclave baskets a zig-zag path as indicated by the broken line 120 in FIGURE 1. This zig-zag path for the heat transfer fluid gives a scrubbing action to the fluid and accomplishes maximum heat transfer in minimum time.

From FIGURES 1 and 3 it will be noted that the baskets 35-38 that support the laminate assemblies W during the laminating process are substantially open frames of octagonal plan configuration. These baskets 35-38 have a pair of spaced bottom support bars 95 that are carried by an open peripheral frame 97. The bottom support bars mount rockable spacer bars 96 that keep the assemblies W spaced so that the heat transfer fluid passed vertically through baskets can pass freely across opposite sides of the assemblies W.

While laminating has occasionally been accomplished in a steam or dry autoclave as opposed to the wet or oil autoclave, still, the complete process has most frequently involved a multi-step rather than a continuous process. The first step usually involved a prepress or tacking step using nipper rolls or the like, or some type of bagging operation carried on in a pressure chamber. Thereafter the individual prepressed laminate assemblies were then transferred to an autoclave unit for the second and final step of completing and curing the bond between the interlayer and the spaced outside sheets. Most frequently some type of handling of the laminate assemblies was required after the prepress step and before the final cure step. Also, the fact that the assemblies had to be cooled after the completion of the bonding step required additional time in the final stage autoclave that elongated the period of the lamin-ating cycle. Each of the noted disadvantages of prior known laminating procedures for glass or similar materials has been eliminated by the continuous multistage process that has been described. In this process and with the disclosed apparatus it is possible to eliminate all individual handling of the laminate assemblies from the time the assemblies are first prepared for prepressing until completion of the laminating cycle and the cooling step. Not only is the disclosed process a continuous process that eliminates handling of the laminate assemblies during the process but the same equipment is used for prepressing final bonding and curing and for cooling. In addition, the heat transfer coils 47-49 and 66 serve duel functions and materially reduce the cycle time for the process. Also, the autoclave apparatus with its novel circulation system for the air or gas, or other fluid that is used as the heat transfer medium, insures a uniform temperature throughout all parts of the autoclave tank and thus all laminate assemblies will be treated in the identical manner so that the yield of the process will be at maximum.

What is claimed is:

1. A continuous multist-age process for laminating an assembly composed of a pair of matched glass sheets and a thermoplastic interlayer comprising enclosing the periphery of the assembly with an endless grooved evacua tion ring that has the groove thereof extending lengthwise of and in open communication with the end edge of the assembly, placing said ringed assembly in a closed container, as the first stage connecting said evacuating ring to an evacuation source and withdrawing air so as to reduce the pressure about the periphery of said assembly to less than atmospheric, pressurizing the fluid medium within said container to a first relatively low pressure head, and applying heat to the fluid medium within said container for a predetermined time to heat said fluid medium to a first predetermined temperature sufficient to create a bond between said interlayer and said glass sheets, then as the second stage discontinuing the evacuation at the end edges of the ringed assembly, increasing the pressure of the fluid medium in the container to a second relatively high value, and at the same time increasing the temperature of the fluid medium in the container to a second temperature sutficient to cure the bond between the glass sheets and the thermoplastic interlayer, and as the third stage relieving the pressure head in said container and discontinuing the heating of the fluid medium in the container.

2. A continuous multistage process for laminating an assembly composed of a pair of matched glass sheets and a thermoplastic interlayer comprising enclosing the periphery of the assembly with an endless grooved evacuation ring that has the groove thereof extending lengthwise of and in open communication with the end edge of the assembly, placing said ringed assembly in a closed container, as the first stage connecting said evacuating ring to an evacuation source and withdrawing air so as to reduce the pressure about the periphery of said assembly to less than atmospheric pressurizing the fluid medium within said container to a first relatively low pressure head, applying heat to the fluid medium within said container to heat said fluid medium to a first predetermined temperature and circulating the heated fluid medium over the assembly for a predetermined time suflicient to create a bond between said interlayer and said glass sheets, then as the second stage discontinuing the evacuation at the end edges of the ringed assembly, increasing the pressure of the fluid medium in the container to a second substantially higher value, and at the same time increasing the temperature of the fluid medium in the container to a second predetermined higher temperature while continuing the circulation of the heated fluid medium over the assembly for a time sumcient to cure the bond between the glass sheets and the thermoplastic interlayer, and as the third stage relieving the pressure head in said container and discontinuing the heating of the fluid medium in the container while activating means to cool the laminated assemblies.

3. A continuous multistage process for laminating an assembly composed of a pair of matched glass sheets and a thermoplastic interlayer comprising enclosing the periphery of the assembly with an endless grooved evacuation ring that has the groove thereof extending lengthwise of and in open communication with the end edge of the assembly, placing said ringed assembly in a closed container, as the first stage connecting said evacuating ring to an evacuation source and withdrawing air so as to reduce the pressure about the periphery of said assembly to below atmospheric pressure in the range of about 20-29 inches of mercury, pressurizing the fluid medium within said container to a first pressure in the range of about 50-100 pounds per square inch, applying heat to the fluid medium within said container to heat said fluid medium to a first predetermined temperature in the range of about 200-265 F. and circulating the heated fluid medium over the assembly for a predetermined time in the range of about 20-30 minutes to create a bond between said interlayer and said glass sheets, then as the second stage discontinuing the evacuation at the end edges of the ringed assembly while retaining the evacuation ring on the assembly, increasing the pressure of the fluid medium in the-container to a pressure in the range of about 250-300 pounds per square inch, and at the same time increasing the temperature of the fluid medium in the container .to a temperature in the range of about 250-300 F. while continuing the circulation of the heated fluid medium over the assemblytor a time in the range of about 25-35 minutes that is suflicient to cure the bond between the glass sheets and the thermoplastic interlayer, and as the third stage relieving the pressure head in said container to atmospheric pressure while retaining the evacuation ring on the assembly without evacuation and discontinuing the heating of the fluid medium in the container while activating means to cool the laminated assemblies to approximately lO-l50 F. by cooling the fluid medium and circulating the cooled fluid medium over the laminate assembly.

a thermoplastic interlayer comprising enclosing the periphery of the assembly with an endless grooved evacuation ring that has the groove thereof extending lengthwise of and in open communication with the end edge of the assembly, placing said ringed assembly in a closed, air filled, container, as the first stage connecting said evacuating ring to an evacuation source and withdrawing air so as to reduce the pressure about the periphery of said assembly to less than atmospheric, pressurizing the air medium within said container to a first relatively low pressure head, and applying heat to the air medium within said container to heat said air to a first predetermined temperature, circulating said heated, pressurized air across said assembly by positive air flow circulation means for a predetermined time to create a bond between said interlayer and said glass sheets, then as the second stage discontinuing the evacuation at the end edges of the ringed assembly, increasing the pressure of the air medium in the container to a second relatively high value, and at the same time increasing the temperature of the air medium in thercontainer to a second predetermined higher temperature while continuing the circulation of the heated, pressurized air across the assembly for a predetermined time to cure the bond between the glass sheets and the thermoplastic interlayer, and as the third stage relieving the pressure head insaid container and discontinuing the heating of the air medium in the container.

5. A continuous multistage process for laminating a group of assemblies each composed of a pair of matched glass sheets and a thermoplastic interlayer comprising enclosing the periphery of each of. the assemblies with an endless groove evacuation ring that has the groove thereof extending lengthwise of and in open communication with the end edge of. the associated assembly, placing said ringed assemblies in a plurality of open baskets with the assemblies in each basket arranged in spaced, upright, positions, arranging said baskets in vertically stacked relationship in a closed container, as thefirst stage connecting each of said evacuating rings to an evacuation source and withdrawing air so as to reduce the pressure about the periphery of said assembly to less than atmospheric, pressurizing the fluid medium within said container to a first relatively low pressure head, applying heat to the fluid medium within said container to heat said fluid medium to a first predetermined temperature and circulating said heated fluid medium through said baskets and across said assemblies in a substantially vertical direction to create a bond between the interlayer and the glass sheets of each assembly, then as the second stage discontinuing the evacuation at the end edges of the ringed assemblies, increasing the pressure of the fluid medium in the container to a second relatively high value, and at the same time increasing the temperature of the circulating fluid medium in the container to a second temperature sufiicient to cure the bond between the glass sheets and the thermoplastic interlayer of each assembly, and as the, third stage relieving the pressure head in said container and discontinuing the heating of the fluid medium in the container while activating means to cool the fluid medium being circulated across the assemblies within the container.

6. In a process as set forth in claim 5 wherein the upright assemblies in adjacent stacked baskets in said container are tilted in opposite directions so that the fluid medium that is passed vertically throughsaid baskets has a zig-zag flow path.

7. A continuous multistage process for laminating a plurality of assemblies each composed of a pair of matched glass sheets and a thermoplastic interlayer comprising enclosing the periphery of each of the assemblies with an endless grooved evacuation ring that has the groove thereof extending lengthwise of and in open communication with the end edge of the assembly, placing said ringed assemblies in open racks in upstanding spaced relationship to each other, vertically stacking the assembly loadedracks in a closed, air filled container, as the first stage connecting the evacuating ring on each assembly to an evacuation source and withdrawing air so as to reduce the pressure about the periphery of said assembly to below atmospheric pressure-in the range of about 20-29 inches of mercury, pressurizing the air within said container to a first pressure in the range of about 50-100 pounds per square inch, applying heat to the airy within said container to heat said air to a first predetermined temperature in the range of about 200-265 F. and circulating the heated air vertically through the racks and over the assemblies for a predetermined time in the range of about 20-30 minutes to create a bond between said interlayer and said glass sheets, then as the second stage discontinuing the evacuation at the end edges of the ringed assembly while retaining the evacuation ring on the assemblies, increasing the pressure of the heated air in the con- 7 tainer to a pressure in the range of about 250-300 pounds per square inch, and at the same time increasing the temperature of the heated air in the container to a temperature in the range of about 250-300 F. while continuing the circulation of the heated fluid medium over the assemblies for a time in the range of about 25-35 minutes that is suflicient to cure the bond between the glass sheets and the thermoplastic interlayer, and as the third stage relieving the pressure head in said container to atmospheric pressure while retaining the evacuation ring on the assembly without evacuation and discontinuing the heating of the air circulating in the container while activating means to cool the laminated assemblies to approximately IOU- F. by cooling the container air and circulating the cooled air vertically through the racks and over the laminate assemblies.

References Cited UNITED STATES PATENTS 1,939,998 12/1933 Lytle 156--382 1,942,624 1/1934 Upton 23290.5 2,027,131 1/1936 Upton 23290.5 2,374,040 4/1945 Ryan 156-404 2,382,956 8/1945 Boicey et al 156-104 2,965,527 12/1960 Morris l56l04 2,992,953 7/1961 Talburtt 156-104 EARL M. BERGERT, Primary Examiner.

ALEXANDER WYMAN, MORRIS 'SUSSMAN,

Examiners; W. J. VAN BALEN, Assistant Examiner. 

1. A CONTINUOUS MULTISTAGE PROCESS FOR LAMINATING AN ASSEMBLY COMPOSED OF A PAIR OF MATCHED GLASS SHEETS AND A THERMOPLASTIC INTERLAYER COMPRISING ENCLOSING THE PERIPHERY OF THE ASSEMBLY WITH AN ENDLESS GROOVED EVACUATION RING THAT HAS THE GROOVE THEREOF EXTENDING LENGTHWISE OF AND IN OPEN COMMUNICATION WITH THE END EDGE OF THE ASSEMBLY, PLACING SAID RINGED ASSEMBLY IN A CLOSED CONTAINER, AS THE FIRST STAGE CONNECTING SAID EVACUATING RING TO AN EVACUATION SOURCE AND WITHDRAWING AIR SO AS TO REDUCE THE PRESSURE ABOUT THE PERIPHERY OF SAID ASSEMBLY TO LESS THAN ATMOSPHERIC, PRESSURING THE FLUID MEDIUM WITHIN SAID CONTAINER TO A FIRST RELATIVELY LOW PRESSUURE HEAD, AND APPLYING HEAT TO THE FLUID MEDIUM WITHIN SAID CONTAINER FOR A PREDETERMINED TIME TO HEAT SAID FLUID MEDIUM TO A FIRST PREDETERMINED TEMPERATURE SUFFICIENT TO CREATE A BOND BETWEEN SAID INTERLAYER AND SAID GLASS SHEETS, THEN AS THE SECOND STAGE DISCONTINUING THE EVACUATION AT THE END EDGES OF THE RINGED ASSEMBLY, INCREASING THE PRESSURE OF THE FLUID MEDIUM IN THE CONTAINER TO A SECOND RELATIVELY HIGH VALUE, AND AT THE SAME TIME INCREASING THE TEMPERATURE OF THE FLUID MEDIUM IN THE CONTAINER TO A SECOND TEMPERATURE SUFFICIENT TO CURE THE BOND BETWEEN THE GLASS SHEETS AND THE THERMOPLASTIC INTERLAYER, AND AS THE THIRD STAGE RELIEVING THE PRESSURE HEAD IN SAID CONTAINER AND DISCONTINUING THE HEATING OF THE FLUID MEDIUM IN THE CONTAINER. 